The Grim Adventures of Billy & Mandy

The Really Odd Couple (2x9)

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Billy accidentally sets off a powerful stink bomb in Mandy's house and, while the house is being disinfected, Mandy's family goes to live with Billy's. Then, Billy and Mandy have a dispute over how to split Billy's room, prompting Grim to intervene. In the end, Mandy takes over the entire room, and traps Billy behind a brick wall.